Sags

A sag is a reduction of AC voltage for a duration of 0.5 cycles to one minute of time. Sags are usually the result of heavy load startups. Typical causes of sags include starting up of large equipment such as large motors or HVAC units that might be connected to the same internal power distribution line in the facility. For example, a motor can draw up to six times normal running current during startup. This type of sudden load will obviously impact the rest of the circuit that the large equipment resides on. At home, sometimes you will notice an impact on your lights when something with a high draw is plugged in.

Sags are the foremost power quality problem encountered in industrial applications, because they frequently cause the interruption of manufacturing processes. Sags can result in a significant economic loss due to rejected products. To resolve these problems, industrial consumers often install voltage sag compensators in critical industrial applications. However, these compensating techniques are expensive and at times ineffective if not designed with proper understanding of the sag’s nature. The transformer, which is usually mounted in front of the critical load, is likely to be exposed to voltage sag. As a result, when the compensator reinstates the load voltage, a serious magnitude of transient current begins to flow toward the sensitive load. This inrush current can either damage the equipment or activate the protection devices. In either case, the compensation will eventually fail. MachineSense Power Analyzer tracks both sag and inrush currents. Industrial operators should be able to monitor both sag and inrush current to make sure neither is affecting their production line.

This under-voltage condition often known by others as a “brownout” condition can create overheating of electrical motors and can also ultimately cause failure of computer power supplies or other electronic equipment including PLCs, robots, as well as servo and VFD drives.

MachineSense Power Analyzer identifies these sags or under voltages so you can understand what’s happening within your electrical circuit. Armed with this information you can easily understand what components that are causing the condition—and rectify the problem.